Abstract: To give full play to the PAI-k-MFV picker’s advantage of parameter adaptive,and improve the correct pick-ing rate and pick accuracy of P-wave arrival time,a modified PAI-k-MFV picker was proposed on the basis of STA /LTA picker and the modified most frequent value criterion. Firstly,a P-wave arrival time set was calculated with the PAI-k picker according to preset the value range and step of window length and confidence probability. Secondly,the interval of P-wave arrival time was searched by STA / LTA picker,and the arrival times that were not in this interval were screened out. Finally,the P-wave arrival time was determined based on the updated arrival time set according to the modified most frequent value criterion. The modified picker preserves PAI-k-MFV picker’s characteristic of adap-tive parameter,without too much parameter tuning,and overcomes the problems of the failure of MFV criterion and the picking points lagging behind the true P-wave arrival time. Compared with other pickers,the modified picker has an obvious advantage in picking P-wave arrival time of microseismic signal with strong background noise and weak micro-seismic signal. The modified picker and PAI-k-MFV picker were applied to pick P-wave arrival time of 115 Dongguas-han microseismic signals with low SNR. The result indicates that the correct picking rate of the modified picker is 96． 52% considering the manual picking results as a benchmark and the time difference within 5 ms that correspond to 30 sampling points as a correct pick,and the correct picks’ mean absolute value is 1. 1 ms,and the standard deviation is 1. 0 ms. The correct picking rate and the picking precision of the modified picker significantly increase comparing to PAI-k-MFV picker.